The BX4500H Bass amp head is listed as 4 ohm/450 watt.
The BX4500H is an Ashdown copy and is very reliable with really good tonal control. I have the pedal (included) that is used to switch on the low(ultrabass akin to an octave) and shape options, which I never used.
It's quite solid, clean, not gross or stinky, and reliable for gigs.